well there isn't much discussion for the 17~85 because of its CA and some barrel distortion
i would like to remind you that the 15~85 owns the IQ of 17~85 hands down, and wider too!! :bigeyes::bigeyes:
you can go to the digital picture and compare the lab shots between the two
well as for the dilemma between the 15~85 and 17~55
ask yourself these questions:
do you shoot often at low light?
what are you looking for your upgrade from your kit lens?
is the kit lens of sufficient focal length to you? (if not the 17~55 might not be good for you since its focal length is similar)
is the high ISO of your camera good?
if you still can make a decision after the above questions
you might want to wait for reviews to come out and look at its build
I must admit I don't often shoot in low light and 1 of the main reason to upgrade is there are moments during shooting when the tele / wide is just not sufficient for coverage and I would start wishing for a longer zoom and wider lens. Haha.....
Thanks for the enlightening, believe I know which lens to buy now.

40D max iso is 1600, good enough for me. :thumbsup: